TY - JOUR
T1 - MOBSTER - VII. Using light curves to infer magnetic and rotational properties of stars with centrifugal magnetospheres
AU - Berry, I. D.
AU - Shultz, M. E.
AU - Owocki, S. P.
AU - Ud-Doula, A.
N1 - Publisher Copyright:
© 2023 The Author(s).
PY - 2023/8/1
Y1 - 2023/8/1
N2 - Early-type B stars with strong magnetic fields and rapid rotation form centrifugal magnetospheres (CMs), as the relatively weak stellar wind becomes magnetically confined and centrifugally supported above the Kepler co-rotation radius. CM plasma is concentrated at and above the Kepler co-rotation radius at the intersection between the rotation and magnetic field axis. Stellar rotation can cause these clouds of material to intersect the viewer's line of sight, leading to photometric eclipses. However, for stars with strong magnetic fields and rapid rotation, CMs can become optically thick enough for emission to occur via electron scattering. Using high-precision space photometry from a sample of stars with strong H α emission, we apply simulated light curves from the rigidly rotating magnetosphere model to directly infer magnetic and rotational properties of these stars. By comparing the values inferred from photometric modelling to those independently determined by spectropolarimetry, we find that magnetic obliquity angle β, viewer inclination i, and critical rotation fraction W can be approximately recovered for three of the four stars studied here. However, there are large discrepancies between the optical depth at the Kepler radius τK expected from magnetometry, and the values required to match the observations. We show that τK of order unity is needed to reasonably match the light-curve morphology of our sample stars.
AB - Early-type B stars with strong magnetic fields and rapid rotation form centrifugal magnetospheres (CMs), as the relatively weak stellar wind becomes magnetically confined and centrifugally supported above the Kepler co-rotation radius. CM plasma is concentrated at and above the Kepler co-rotation radius at the intersection between the rotation and magnetic field axis. Stellar rotation can cause these clouds of material to intersect the viewer's line of sight, leading to photometric eclipses. However, for stars with strong magnetic fields and rapid rotation, CMs can become optically thick enough for emission to occur via electron scattering. Using high-precision space photometry from a sample of stars with strong H α emission, we apply simulated light curves from the rigidly rotating magnetosphere model to directly infer magnetic and rotational properties of these stars. By comparing the values inferred from photometric modelling to those independently determined by spectropolarimetry, we find that magnetic obliquity angle β, viewer inclination i, and critical rotation fraction W can be approximately recovered for three of the four stars studied here. However, there are large discrepancies between the optical depth at the Kepler radius τK expected from magnetometry, and the values required to match the observations. We show that τK of order unity is needed to reasonably match the light-curve morphology of our sample stars.
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U2 - 10.1093/mnras/stad1726
DO - 10.1093/mnras/stad1726
M3 - Article
AN - SCOPUS:85165056309
SN - 0035-8711
VL - 523
SP - 6371
EP - 6385
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -